The proposed Phase I research is intended to evaluate and demonstrate the feasibility of making accurate noninvasive and continuous measurements of arterial blood gases (p02, pC02, and pH) in a single device, utilizing the oral mucosa as a unique and optimal site for these measurements. Innovative sensor features will be evaluated in vitro and with human volunteers. Advanced technology previously developed by RAI for the oral measurement of p02 will be applied to modify presently available pC02 and pH sensors to permit oral use and achieve high accuracy of arterial blood-gas measurements. A miniaturized sensor module containing sensors for all three blood gases will be designed incorporating this technology and fitting easily and inobtrusively into the mouth. This sensor module found in any other devices; in particular, measurement accuracies which essentially equal those of blood gas machines are anticipated. The proposed research will define these clinical advantages along with the suitability of this concept to various patient types and clinical uses. This system is expected ton be equally applicable to infant, pediatric, adult, and aged patients.